1. Field of the Invention
The present invention relates to low melting point glass, an insulating package, and a sealing member which are preferable for quartz oscillators, more specifically, low melting point glass, an insulating package, and a sealing member for secure sealing.
2. Description of the Related Art
In accordance with the recent tendency of compactness, weight reduction, and surface mounting of electronic parts, also in the quartz oscillators, the cylindrical metal package has been changed to a ceramic package. A typical type thereof shall be described below.
FIG. 1A through FIG. 1C show a conventional surface mounting type quartz oscillator G, wherein FIG. 1A is a plan view partially cut and opened, FIG. 1B is a longitudinal section along the centerline in the length direction, and FIG. 1C is a lower view.
In the conventional surface mounting type oscillator G, bottom plate 101 and frame body 102, which are made of ceramic, are formed and united to comprise insulating base 115. The bottom plate 101 has the shape of a plate. The shape of the frame body 102 has the shape of a frame.
At the upper surface of one end in the length direction of the bottom plate 101, as shown in FIG. 1A, an Ag/Pb paste is applied and sintered, whereby Ag/Pb electrodes 103 and 104 are formed. The Ag/Pb electrode 103 is led to the outside from one end in the length direction of the bottom plate 101 by passing between the bottom plate 101 and frame body 102 as shown in FIG. 1B. The other Ag/Pb electrode 104 is, as shown in FIG. 1B, led to the outside from the other end of the bottom plate 101 by making a detour below the frame body 102. Also, at both ends in the length direction of the lower surface of the bottom plate 101, Ag/Pb terminals 105 and 106 are formed. The Ag/Pb electrodes 103 and 104 are connected to the Ag/Pb terminals 105 and 106 through the end face of the bottom plate 101, respectively. On the Ag/Pb electrodes 103 and 104 and Ag/Pb terminals 105 and 106, electroless Ni plating layer and/or electroless Au plating layer are formed although it is not shown.
On the Ag/Pb electrodes 103 and 104, quartz oscillating piece 108 having electrodes (not shown) on both surfaces are adhered by an electric conductive adhesive, and the Ag/Pb electrodes 103 and 104 and quartz oscillating piece 108 are connected to each other.
Also, near the end portion of the opposite side of the Ag/Pb electrodes 103 and 104 at the upper surface of the bottom plate 101, support 107 for supporting the quartz oscillating piece 108 in a horizontal condition is formed. The support 107 is called xe2x80x9cpillowxe2x80x9d in some cases.
On the frame body 102, ceramic-made cap 110 is adhered via low melting point glass 109. Thereby, the inside of the insulating package is sealed.
However, the surface mounting type quartz oscillator G has a serious problem in that, since the bottom plate 101, frame body 102, and cap 110 are formed from ceramic, due to a difference in the thermal expansion coefficient from quartz oscillating piece 108, stresses are added to the quartz oscillating piece 108, whereby the vibration characteristics are changed.
Also, if the cap 110 made of ceramic is used, in view of the mechanical strength, there is a limit to make the vibrator thinner. Therefore, there are also limits to making the entire quartz oscillator G smaller in height.
Therefore, the present applicant proposed that the insulating base was made of a glass ceramic compound, and in place of the ceramic-made cap, a metal cap made of stainless steel was used. FIG. 2A through FIG. 2C show a conventional surface mounting type quartz oscillator H, wherein FIG. 2A is a plan view partially cut and opened, FIG. 2B is a longitudinal section along the centerline in the length direction, and FIG. 2C is a lower view.
In the conventional surface mounting type quartz oscillator H, bottom plate 121 and frame body 122 which are made of a glass ceramic compound are formed and united to comprise insulating base 135. Also, on the frame body 122, via low melting point glass 109, metal cap 130 made of stainless steel is adhered. The other structure is the same as in that of the surface mounting type quartz oscillator G.
The glass ceramic compound is formed by dispersing fine powder of forsterite of 30 through 70 wt % in alkali glass, and its thermal expansion coefficient is 100xc3x9710xe2x88x927 through 150xc3x9710xe2x88x927 (/xc2x0 C.). By using such glass ceramic, the difference in the thermal expansion coefficient between the quartz oscillating piece and metal cap is eliminated or remarkably reduced. Therefore, the change in characteristics of the quartz oscillating piece and separation of the metal cap due to the stress caused by the difference in the thermal expansion coefficient can be prevented.
However, when such a quartz oscillator was stored at a high temperature and in high humidity, a phenomenon in that separation occurred between the frame body and low melting point glass was shown.
The object of the invention is to provide low melting point glass, an insulating package, and a sealing member whereby secure sealing can be made between an insulating base and a cap.
According to one aspect of the present invention, low melting point glass contains at least one kind selected from a group consisting of Al, Ni, Ag, BaTiO3, NiCr, TiB, and TiO2.
The inventors thoroughly researched the cause for the abovementioned phenomenon, and as a result, they found that the alkali glass composing the glass ceramic caused elution of the phosphoric acid composing the low melting point glass, and the composition of the low melting point glass changed and its sealing performance was lost, whereby separation occurred. Also, they thoroughly researched a method for preventing such a phenomenon, and as a result, they found that, by adding certain kinds of additives to the low melting point glass, the phenomenon could be prevented.
The abovementioned low melting point glass has an action whereby elution of phosphoric acid from the low melting point glass due to the alkali glass ingredients in the glass ceramic is suppressed or prevented by the additive, and the low melting point glass can be directly sealed with the glass ceramic.
According to a second aspect of the present invention, a glass ceramic sealing member comprises a base member made of a glass ceramic compound, and low melting point glass to be used to seal the base member. The low melting point glass contains at least one kind of substance selected from a group consisting of Al, Ni, Ag, BaTiO3, NiCr, TiB, and TiO2.
In this aspect of the invention, elution of phosphoric acid in the low melting point glass due to the alkali glass ingredients in the glass ceramic is suppressed or prevented by the additive in the low melting point glass, whereby the glass ceramic sealing member can be increased in airtightness.
According to a third aspect of the present invention, a sealing member comprises a base member made of ceramic, low melting point glass to be used to seal the base member, and a buffer layer interposed between the base member and the low melting point glass.
In the aspect of the invention, by a buffer layer interposed between the ceramic and low melting point glass, mutual interference under storage at a high temperature and in high humidity is prevented, elution of phosphoric acid in the low melting point glass due to the alkali ingredients in the ceramic does not occur, and lowering in peel-strength at the sealing interfaces can be prevented, whereby separation does not occur.
According to a fourth aspect of the present invention, an insulating package comprises an insulating base having a bottom plate and frame body, electrodes led out from the inside to the outside of the insulating base, a metal cap which seals the frame body, and low melting point glass to adhere said metal cap to the frame body. The low melting point glass has spherical particles with diameters of 10 xcexcm or more dispersed inside.
In the aspect of the invention, due to spherical particles dispersed in the low melting point glass, the dimension of the space between the upper surface of the frame body and lower surface of the cap is easily and securely restricted, and inclination of the metal cap is prevented, whereby the package can be reduced in height more than in the prior-art.
According to a fifth aspect of the present invention, an insulating package comprises an insulating base having a bottom plate and frame body, electrodes led from the inside to the outside of the insulating base, a conductive cap which seals the frame body. The conductive cap has a cap core and a conductive film which is formed at least at the lower surface of the cap core and has resistance lower than that of the cap core.
In the aspect of the invention, by an electric conductive film and electric conductive sealing material formed at least at the lower surface of the electric conductive cap body, the electric conductive cap can be grounded at low resistance.
According to a sixth aspect of the present invention, an electronic element sealing member comprises an insulating package as set forth in claim 26, and a quartz oscillating piece or piezoelectric material element sealed within the insulating package as an electronic element.
In the aspect of the invention, the characteristics of the quartz oscillating piece or piezoelectric material element housed in the structure do not change due to the floating capacity and external electromagnetic waves.